Alpha and beta radiation producing isotopes are utilized or produced in many fields and, while not as high in ionizing and penetrating power as other forms of radiation, still present health dangers and must be handled and disposed of accordingly. For instance, radionuclides common in transuranic waste (TRU) can produce high levels of both alpha and beta radiation. TRU is generally defined as waste that has been contaminated with transuranic radionuclides (i.e., possessing atomic numbers greater than that of uranium) in concentrations greater than 100 nCi/g (3.7 MBq/kg). In the U.S. TRU is generally a byproduct of weapons production, nuclear research and power production, and includes protective gear, tools, residue, debris and other items contaminated with small amounts of radioactive elements. TRU contains such radionuclides as Californium (Cf-249, Cf-252), Americium (Am-241, Am-242, and Am-243), Curium (Cm-242, Cm-250), Neptunium (Np-235, Np-236), Plutonium (Pu-236, Pu-238, Pu-239, Pu-242) and Berkelium (Bk-247, Bk-250), as well as their respective decay products.
Under U.S. law, TRU is categorized into “contact-handled” (CH) and “remote-handled” (RH) on the basis of the radiation field measured on the waste container's surface. CH-TRU has a surface dose rate not greater than 2 mSv per hour (200 mrem/h), whereas RH-TRU has rates of 2 mSv/h or higher. CH-TRU has neither the high radioactivity of high level waste nor its high heat generation as CH-TRU waste emits mostly alpha radiation and relatively small levels of beta radiation, but it is still potentially harmful, particularly due to inhalation hazards.
Of course, TRU is not the only material that produces alpha and/or beta radiation and requires controlled handling and storage. Other alpha emitting sources include radium, thorium, actinium, and uranium to name a few. Additionally, strontium (e.g., SR-90), which undergoes beta decay, is commonly used as a radioactive source in cancer therapy and as a radioactive tracer in both medical and agricultural applications. Tritium, primarily produced in nuclear power generation systems, also undergoes beta decay, and the radium isotope Ra-223 that has been approved by the FDA in cancer treatment emits primarily alpha and beta particles.
These and other alpha and beta particle emitting materials present serious issues with regard to proper handling and disposal. For instance, the use of medicinal grade radioactive solutions (e.g., Sr-90) is undergoing great expansion. Military use of radioactive materials creates additional levels of radioactive waste that must be safely handled, stored, transported, and disposed of. Safety issues also exist in decommissioned uranium/plutonium enrichment plants, which have left behind contaminated soils, equipment, and wastes that have to be properly disposed of. Moreover, utilities continue to create significant amounts of nuclear waste from power generation plants.
While alpha/beta radiation does not require a heavy lead shielding, it still presents challenges for safe storage and containment. Exposure to alpha and beta radiation can induce chronic, carcinogenic and mutagenic health effects that lead to cancer, birth defects, and death. One of the main hazards of alpha radiation is its potential for exposure by inhalation or ingestion. Inhalation of such materials even in very small quantities can deliver a significant internal radiation dose. Tons of solid, liquid, and sludge radioactive wastes have been generated and they will continue to be generated in the future by commercial and private industries as well as government agencies. These materials must be safely and cost effectively shielded, managed, and disposed of, to prevent health and economic consequences to the global environment.
Current shielding used for radiation/nuclear applications and general radiation and nuclear protection includes solid constructed structures that are large and extremely heavy. These conventional shielding structures are difficult to transport and are typically permanent structures that require substantial installation time and costs.
More flexible and transportable containment systems have been developed, but these systems generally require multiple individual layers of different materials to increase mechanical and containment properties and storage/transport systems generally involve placing the waste material into two or more polymeric containers (e.g., bags) and then storing the multi-layer containers in metal containers as the polymeric materials exhibit less than ideal resistance to radiological degradation and mechanical forces. For instance, currently utilized polymeric containment systems tend to show little resistance to radiolysis leading to the decomposition of the polymers and hydrogen production, which can cause both flammability and over pressurization hazards. Moreover, due to short life span of the containers, re-packaging of the waste is often required, which increases the occupational dose to the workers as well as risk to both the workers and the environment, particularly as re-packaging is often carried out only after degradation has been detected and the containment field of the bag has been compromised.
What are needed in the art are containment materials that exhibit increased resistance to radiological degradation events, and in particular alpha and beta particle emission. Containment materials that can signal effects of degradation prior to compromise of the containment field of the container would also be of great benefit.